On a 2G/3G (Second Generation Third Generation) GPRS (General Packet Radio Service) network, an SGSN (Serving GPRS Support Node) accesses an HLR (Home Location Register) through a MAP-based Gr interface, and an ISDN (Integrated Services Digital Network) number is used to address each network element node on the GPRS network. However, on an evolved 4G (Fourth Generation) LTE (Long Term Evolution) network, an MME (Mobility Management Entity) accesses an HSS (Home Subscriber Server) through a Diameter-based S6a interface, and a host name/domain name is used to address each network element on the LTE network. Therefore, when an LTE subscriber roams to a GPRS network, an IWF (Interworking Function) needs to implement conversion from the MAP (Mobile Application Part) protocol to the Diameter protocol, so that access authentication and location management can be performed for the subscriber and further the SGSN network element can acquire corresponding subscriber data from the HSS. Conversely, when a GPRS subscriber roams to an LTE network, the IWF needs to implement conversion from the Diameter protocol to the MAP protocol, so that access authentication and location management can be performed for the subscriber and further the MME network element can acquire corresponding subscriber data from the HLR.
An IWF is deployed on an LTE network, and if an ISDN number or a domain name/host name of an SGSN/HLR on a GPRS network of an operator needs to be acquired, a correspondence between the ISDN number and the domain name/host name of the SGSN/HLR of the operator needs to be preconfigured on the IWF. For these reasons, when an additional SGSN/HLR is set up on a GPRS network of another operator who does not run the LTE network, the IWF is probably not notified of the additional SGSN/HLR, that is to say, a correspondence between an ISDN number and a domain name/host name of the additional SGSN/HLR is not configured on the IWF. Consequently, roaming cannot be implemented for subscribers served by the additional SGSN/HLR.